The five bodies selected for this review represent the latest developments in APS-C sensors. They all possess high-definition figures, with 16 megapixels packed on the sensor and even 18 for the EOS 60D. These cameras also have another point in common: they all display very wide ISO latitudes, ranging from ISO 100 to 12800, 25600, and even 51200 for the Pentax K5. On the spec sheets at least, these figures are impressive, and suggest avery good behavior in low-light environments, perhaps better than for some “ancient” full-frame bodies.

First we will analyze these cameras’ DxO Use Case scores to see which tendencies they reveal. We will then dig deeper in our examination of the SNR and dynamic range metrics that are crucial to this study. And since these APS-C sensors are new, it is legitimate to ask how they compare with their predecessors… and with full-frame sensors.

a55: the audacious choice of a semi-transparent mirror

If the sensors all look roughly similar in their specifications, the Alpha 55 uses a radically different technology than the others bodies with its implementation of a semi-transparent mirror. The technology itself is not new: film cameras such as the Canon Pellix used this kind of mirror back in 1965.

The principle is simple: when light strikes the semi-transparent mirror, 70% manages to go through it, while the remaining 30% is deflected on the AF detection array. There are several advantages for the Alpha 55: the mirror does not move anymore, allowing much faster burst speeds (the Alpha 55 is actually the fastest one by far among the five cameras, reaching an impressive 10 fps); this technology also allows direct and constant live-view operation. While helpful for video operation, the bottom line for photography is that the amount of light hitting the sensor is reduced compared to a camera using a conventional mirror. This can pose problems, especially under low-light conditions, and it is probably the cause of a higher noise level. —This is, by the way, the main reason why the semi-transparent mirror bodies did not manage to seduce photographers in the past. Is it worth improving one function (the video) if it endangers another crucial one (the photography) ?

Further readings for the DxOMark review for APS-C camera 2010 : who takes the lead ?

To provide photographers with a broader perspective about mobiles, lenses and cameras, here are links to articles, reviews, and analyses of photographic equipment produced by DxOMark, renown websites, magazines or blogs.

We are already acquainted with the D3200: apart from a few ergonomic details, it’s the same camera as the compact and lightweight D3100 SLR, though missing the secondary display on its bridge for even greater compactness. The D3200 weighs only 454 grams (without battery or card). Unlike the D3100, the D3200’s lens is off-center for better balance and the highly practical LiveView/video mode activation tab of the D3100 and the D5100 has disappeared in favor of a more ergonomically mundane video recording button. The D3200 comes with a second (dorsal) infrared sensor to complement its front sensor for more practical infrared remote control. The motor selection tab (single-frame, burst, timer, remote control) is gone as well, again replaced by a direct-access button.

The Nikon D5100 replaces the D5000 in Nikon’s lineup; it finds its place right below the Nikon D7000, according to Nikon’s marketing the D90 is still positioned between the D5100 and the D7000, however the spec sheet and the performances of the D5100 make this hard to believe.

This is because the D5100 shares the same Sony 16 megapixels sensor as the D7000. The major difference between the two bodies being the AF: 11 points with 3D tracking for the D5100 (presumably the “old” MultiCam 1000 already used on the D90) versus the 39 points with 3D tracking now used on the D7000.